The present invention relates to an improved type of electrician's pliers which will simultaneously cut and strip a predetermined length of insulation from a wire.
Specialty pliers which will separately cut wire and strip a length of insulation from the electrical conductor are in common use by electricians. The insulation stripping operation is necessary to expose the conductor when connecting the wire to an appliance or when two or more wires are to be connected. Available pliers range from very simple to relatively complex in construction and function. Most are adapted to operate on a number of different wire sizes. Additionally, some also serve to crimp connectors such as spade lugs to the end of a wire. Formerly, in connecting a wire to a unit the electrician had to make a loop in the conductor end. This is held to the appliance under a screw head. In recent years, switches and wall plugs for home and commercial use have become available, in which it is only necessary to insert a short length of bare conductor into a small opening in the device. There it is held tightly by a pair of miniature jaws. Devices of this type have had a significant impact in reducing the amount of time required for home and commercial wiring.
One requirement common to switches, wall plugs, and other devices of the above type is that the wire must be stripped for a predetermined length. The electrician usually gages this length by eye so that it is rarely precise. If the length of conductor stripped is too short, there is risk that it will not be held tightly in the appliance and may work loose, causing an open circuit. If too great a length of insulation is stripped, bare conductor will be exposed at the connection and this presents a potential hazard of shocks or short circuits. For these reasons, it would be a major advantage to an electrician to have pliers available that would cut wire and strip a precise predetermined length of insulation simultaneously. To the present inventors knowledge, no such pliers are commercially available.
Cortese, in U.S. Pat. No. 3,854,202, shows a pair of electrical pliers forged with cutting jaws similar to those found on end nippers. Each jaw has attached to it by a wing nut, an adjustable insulation cutter, which serves as a stripper. A thumb screw serves as a stop to control jaw closure so that various wire sizes can be stripped without cutting into the conductor. Iff, in U.S. Pat. No. 3,913,425, shows a very complex cutter/stripper. This first severs the end of the wire then cuts into the insulation. An auxiliary pair of jaws then grips and strips the insulation as the handles are squeezed to a full closed position. A simpler and more nearly conventional type of stripper is shown in U.S. Pat. No. 3,872,746, to Wittes et al. This has a pair of conventional longitudinal cutting jaws bearing transverse end-mounted stripper jaws. The stripping operation is adjusted for wire size by a slideable cam mounted on one of the handles. Irwin, U.S. Pat. No. 924,357, shows an early style of lineman's pliers.
Each of the aforementioned types of pliers have certain shortcomings. Those that cut and strip in one operation are unnecessarily complex and expensive, and, in some cases, would be very difficult to adjust precisely. The present invention overcomes the above problems so that the electrician can readily cut and precisely strip a predetermined length of insulation from the end of wire in one rapid operation.